Was just wondering if it's possible to retain a check engine light (CEL) when using any of the aftermarket ECUs? They must be able to tell when a sensor is going bad, or if it's getting bad readings due to a bad tune. I was hoping that an aftermarket ECU can be hooked up to the dash CEL so that you can know right away if there's a problem while driving.

And what about something like the brake & battery indicators going off due to a bad alternator? Is there any way to keep that when you run with an aftermarket ECU?

Rogue-AE95 wrote:Was just wondering if it's possible to retain a check engine light (CEL) when using any of the aftermarket ECUs? They must be able to tell when a sensor is going bad, or if it's getting bad readings due to a bad tune. I was hoping that an aftermarket ECU can be hooked up to the dash CEL so that you can know right away if there's a problem while driving.

And what about something like the brake & battery indicators going off due to a bad alternator? Is there any way to keep that when you run with an aftermarket ECU?

Brake and Battery indicators are separate of the ECU, so that'll work no matter what.

I don't remember about the Megasquirt 2, but the Megasquirt 3 has a method of determining if a sensor is faulty, going into a limp mode, and triggering a light. It's really cool, actually, but involves a LOT of tuning to get right.

Rogue-AE95 wrote:Was just wondering if it's possible to retain a check engine light (CEL)
when using any of the aftermarket ECUs?

To be able to monitor for a bad (out of range) sensor input, the ECU would
have to know the expected sensor range. Easy enough for a factory stock car
with factory sensors and factory ECU. Not so easy when the ECU supplier does
not know what car the ECU will be fitted to, and what type/range of sensors
are used.

Probably why serious race cars are fitted with a full array of gauges to show
operation critical values for temperature, pressure, knock, AFR etc.

If you seriously wanted a CEL, you would need an aftermarket ECU with a lot
of aux inputs and connect up a bunch of sensors to everything that you want
to monitor. Program the ECU to trigger an aux out for the CEL each time a
sensor reading goes high (temp) or low (pressure). If you had two different
tunes, you could have the ECU switch tunes when the CEL output turned on.

I have a very simple ECU and I use it to switch my electric cooling fan on/off
according to the reading of the EWT. With a sophisticated ECU there are a
lot more programming (logic) options.

Cheers... jondee86

Thanks guys. Looks like I have more reading up to do on aftermarket ECUs. Using a chipped Honda ECU seems to have a few advantages in this regard, although it would also be a bit complicated to set up.

Rogue-AE95 wrote:Thanks guys. Looks like I have more reading up to do on aftermarket ECUs. Using a chipped Honda ECU seems to have a few advantages in this regard, although it would also be a bit complicated to set up.

To be honest, I've never found a CEL necessary with an aftermarket ECU. It's really easy to diagnose sensors, injectors, coils, etc. when you have as much control and flexibility as a fully programmable ECU provides.

Rogue-AE95 wrote:Was just wondering if it's possible to retain a check engine light
(CEL) when using any of the aftermarket ECUs?

Here ya go... http://www.adaptronic.com.au/the-basic- ... functions/

Cheers... jondee86

burdickjp wrote:To be honest, I've never found a CEL necessary with an aftermarket ECU. It's really easy to diagnose sensors, injectors, coils, etc. when you have as much control and flexibility as a fully programmable ECU provides.

I bet he needs a working(or appears to be working) CEL for inspection/emissions/registration purposes.

MSPNP owners: does the CEL come on? or can it be triggered via the ecu somehow?

Inquiring minds wanna know.

Very cool, thanks for that link!

Thankfully I don't have inspections to deal with, but if I move someday and have to deal with them, I would need a workaround. I do like having a "dummy" light to let me know something is not kosher in the engine bay. If a sensor fails, like air intake temp, you could have problems with your tune but never know it (because who is going to have a gauge relating to every sensor?). But instead of having to stick a jumper in a diagnostic connector and goof around with codes, you just check your ECU with a laptop (or however you check data logging). Better than OBD-II...

the latest Megasquirt3 firmware uses code based CEL so it actually blinks like the stock car did telling u what is wrong which for me is awesome and yes i use it!
the result is all of my warning lights are still fully functional as are my gauges. but i still run a tablet on shadowdash because it too is awesome!

jmaz87 wrote:the latest Megasquirt3 firmware uses code based CEL so it actually blinks like the stock car did telling u what is wrong which for me is awesome and yes i use it!
the result is all of my warning lights are still fully functional as are my gauges. but i still run a tablet on shadowdash because it too is awesome!

Very cool... thanks.